Posters

Finite element analysis of accommodation biomechanics in young vs presbyopic eyes

Poster Details

First Author: A.Hipsley USA

Co Author(s):    K. Knaus   S. Blemker   D. Goldberg              

Abstract Details

Purpose:

To understand the mechanisms involved with age-related changes in accommodative biomechanics using a Finite Element (FE) model which incorporates key anatomical structures including the sclera, ciliary muscles (CM), crystalline lens, lens capsule, zonules, and choroid.

Setting:

A novel physics-based computer simulation; Biomedical Engineering Department, University of Virginia. Thornton Hall, P.O. Box 400259,  Charlottesville, VA 22904-4259

Methods:

A 3-D model of the eye was constructed using meshing and FEM analysis was performed using advanced multi-physics simulation (AMPS) technology on representative 3D models of ocular structures. Zonular pre-tensioning of the lens was simulated to establish the unaccommodated state and CM contractions were simulated to establish the accommodated state. The CM groups were activated and accommodative power was analyzed as a function of the resulting CM excursion and lens displacement which were then calibrated with published data images (OCT/UBM/MRI) in young(30yrs) and presbyopic(50yrs) eyes. CM fiber groups were activated in isolation to quantify each’s contribution to accommodation biomechanics.

Results:

The model demonstrated multiple components of the accommodative apparatus behave biomechanically to result in CM excursion at the apex inward and shortening of the longitudinal muscle upwards under specific zonular tension in agreement with the Hemholtz. These accommodative biomechanics are also affected by extralenticular structures such as the sclera, choroid, and zonular geometry. The model also revealed specific contributions of ciliary fiber groups to lens changes. Sensitivity analysis of the differences in accommodation between the “young/healthy” and “old/presbyopic” eye identified the age-related changes that contribute most to symptoms of presbyopia.

Conclusions:

FE modeling has shown that accommodative biomechanics require considerations of many anatomical components to understand the normal and age-related functions of the system. Age-related changes in the ocular tissues impede normal CM function as well as capability for lens deformation required for normal accommodative biomechanical function. To overcome age-related changes in the tissues, the CM must increase its activation by as much as 20%. Further analyses utilizing virtual surgical and therapeutic simulations may provide novel insight to new technology applications in presbyopia.

Financial Disclosure:

None